U.S. patent application number 11/141193 was filed with the patent office on 2005-12-15 for optical module and manufacturing method of the same.
This patent application is currently assigned to Toyoda Gosei Co., Ltd.. Invention is credited to Inui, Yukitoshi, Komada, Minoru, Maeno, Takashi, Terada, Kazuhiro.
Application Number | 20050276545 11/141193 |
Document ID | / |
Family ID | 34937142 |
Filed Date | 2005-12-15 |
United States Patent
Application |
20050276545 |
Kind Code |
A1 |
Inui, Yukitoshi ; et
al. |
December 15, 2005 |
Optical module and manufacturing method of the same
Abstract
There is provided a method of manufacturing an optical module
comprises a component fixing step in which an optical waveguide and
at least one optical device are detachably held by a fixing member
capable of holding an uncured light curable resin in a required
position, and a core forming step in which light of a wavelength
for curing the light curable resin is emitted from the leading end
of the optical waveguide to the light curable resin uncured and
thus the light curable resin is cured to form a shaftlike core.
According thereto, the optical waveguide and the optical device are
connected by the core.
Inventors: |
Inui, Yukitoshi; (Aichi,
JP) ; Terada, Kazuhiro; (Aichi, JP) ; Komada,
Minoru; (Aichi, JP) ; Maeno, Takashi; (Aichi,
JP) |
Correspondence
Address: |
MCGINN INTELLECTUAL PROPERTY LAW GROUP, PLLC
8321 OLD COURTHOUSE ROAD
SUITE 200
VIENNA
VA
22182-3817
US
|
Assignee: |
Toyoda Gosei Co., Ltd.
Nishikasugai-gun
JP
|
Family ID: |
34937142 |
Appl. No.: |
11/141193 |
Filed: |
June 1, 2005 |
Current U.S.
Class: |
385/88 ;
385/51 |
Current CPC
Class: |
G02B 6/4246 20130101;
G02B 2006/12164 20130101; G02B 6/138 20130101 |
Class at
Publication: |
385/088 ;
385/051 |
International
Class: |
G02B 006/36 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 2, 2004 |
JP |
P2004-164084 |
Mar 29, 2005 |
JP |
P2005-095568 |
Claims
What is claimed is:
1. A method of manufacturing an optical module comprising: holding
detachably an optical waveguide and at least one optical device by
a mold, holding an uncured light curable resin in the mold;
emitting light of a wavelength for curing the light curable resin
from a leading end of the optical waveguide to the light curable
resin and curing the light curable resin to form a core; and
connecting the optical waveguide and the optical device by the
core.
2. The method of manufacturing an optical module according to claim
1, further comprising: removing an uncured part of the light
curable resin from a surface of the core; and covering the leading
end of the optical waveguide, an exposed surface of the core, and
the optical device with a cladding material.
3. The method of manufacturing an optical module according to claim
2, wherein the mold is detached after the core is formed.
4. The method of manufacturing an optical module according to claim
1, wherein the core is formed after at least one optical component
such as a mirror, a half mirror is held on the mold.
5. The method of manufacturing an optical module according to claim
4, wherein the uncured part of the light curable resin is removed
after the optical waveguide, the optical component, the optical
device, and the core, which is formed so as to integrally connect
therewith and is branched and/or bent, are detached from the
mold.
6. The method of manufacturing an optical module according claim 2,
wherein the cladding material includes a light curable or heat
curable resin, and the exposed surface of the core is covered with
the light curable or heat curable resin uncured, which resin is
thereafter cured.
7. The method of manufacturing an optical module according to claim
4, wherein the optical component and optical device are fixed as
the cladding material covers main portions thereof and as the
cladding material covers a vicinity of an emitting end of the
optical waveguide.
8. An optical module comprising: an optical waveguide; a core that
is formed in a self-forming manner by light curing as light is
emitted from a leading end or the optical waveguide; an optical
device connected to an other end of the core; and a cladding made
of resin cured to integrally cover the leading end of the optical
waveguide, the core, and the optical device.
9. The method of manufacturing an optical module according to claim
1, wherein a mold comprises: an opening in the upper side thereof;
and a drain port which is provided in a bottom of the mold to drain
an uncured resin, wherein an end of the optical waveguide is
inserted into the mold in a horizontal direction, and wherein a
formed resin component and the optical waveguide is detached from
the mold in a state where the resin component and the optical
waveguide are held connected.
10. The method of manufacturing an optical module according to
claim 1, further comprising: inserting one end of the optical
waveguide into the mold in a horizontal direction; putting the
optical device into the mold through an opening of the mold and fix
the optical device temporarily; introducing the light curable resin
into the mold; emitting a light beam at a wavelength adapted to
harden the curable resin, from an other end of the optical
waveguide into the mold, thereby to form the core which extends
from the one end of the optical waveguide inserted into the mold,
to the optical device; opening a drain port in a bottom of the
mold, draining an uncured part of the light curable resin from the
drain port; releasing a temporary fixation of the optical device
connected by the core, and introducing a cladding material into the
mold; curing the cladding material; and taking an optical module
having the optical waveguide and the optical device integrated by
the cladding material out of the mold.
11. The method of manufacturing an optical module according to
claim 9, wherein the curable resin is introduced after any desired
number of reflective mirrors, semitransparent mirrors or other
optical components have been put into the mold through the opening
of the mold and have been temporarily fixed.
12. An apparatus for manufacturing an optical module comprising: a
mold which has an opening above and is capable of draining an
uncured resin from a drain port that is provided in a bottom of the
mold, wherein one end of the optical waveguide is insertable into
the mold in a horizontal direction, and a formed resin component
and the optical waveguide are detachable from the mold in a state
where the resin component and the optical waveguide are connected
to each other; a jig for putting at least one optical device into
the mold through the opening of the mold so as to temporarily fix
the optical device; means for introducing a light curable resin for
forming a core into the mold; means for guiding a light beam at a
wavelength adapted to cure the light curable resin, from another
end of the optical waveguide into the mold; means for introducing a
cladding material into the mold; and means for curing the cladding
material, wherein the optical waveguide and the optical device are
connected by a core formed from the light curable resin, and
covered with the cladding material.
13. The method of manufacturing an optical module according to
claim 1, wherein the optical waveguide is an optical fiber.
Description
[0001] This application is based on Japanese Patent Application No.
2004-164084 and 2005-095568, which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an optical module that has
a core fabricated using a light curable resin solution and light,
and to a method of and an apparatus for manufacturing the optical
module. The invention is applicable to an inexpensive and low-loss
optical module for use in optical fiber communications, such as an
optical transmitter and receiver, an optical interconnection
device, and an optical branching filter or coupler.
[0004] 2. Description of the Related Art
[0005] The inventors, together with their coinventors, have
developed and applied for patent on an optical waveguide having a
so-called self-forming type core. The self-forming type core forms
the optical waveguide in the following manner. That is, for
example, a liquid light curable resin uncured is irradiated with
curing wavelength light in a beam form from an optical fiber.
Thereby, only the resin in an optical path portion irradiated in
the beam form is cured to form a shaftlike cured material (core).
Thereafter, the core is surrounded by a lower refractive index
resin for example, thus forming the optical waveguide (see
JP-A-2002-365459). Besides, the following is shown by using two
light curable resins different in refractive index and curing
wavelength. That is, when only the resin on the high refractive
index side is cured for a long time (see JP-A-2002-169038) and when
only the resin on the low refractive index side is cured for a
short time (see JP-A-2004-149579), the remaining resin solution
uncured is thereafter cured, thereby making it possible to form two
kinds of optical waveguides each having a specific refractive index
distribution.
[0006] The technology related to the invention will be described
using FIGS. 4A to 4E. FIGS. 4A to 4E are process diagrams showing a
method of manufacturing an optical module having one light
receiving device and one light emitting device.
[0007] As shown in FIG. 4A, an open-topped casing 91 made of
transparent resin is prepared, and a core end face 921 of an
optical fiber 92 is introduced into the inside of the casing 91 and
then fixed by a fixing member 93. Next, a half mirror or dichroic
mirror (wavelength selective mirror) 94 is fixed to the casing 91.
The half mirror or dichroic mirror (wavelength selective mirror) 94
is fixed inclined at 45 degrees to the bottom surface of the casing
91. Thereafter, to form a core member, the inside of the casing 91
is filled with a high refractive index light curable resin solution
95 uncured.
[0008] Next, when the light curable resin solution 95 having filled
the casing 91 from the end face 921 is irradiated with the curing
wavelength light by the optical fiber 92, then a cured material 95c
is formed as being shaftlike along the optical path of the light
(FIG. 4B). Since the half mirror or dichroic mirror (wavelength
selective mirror) 94 is used this time, the cured material 95c will
have branches. Thereafter, the light curable resin solution 95
uncured is removed (FIG. 4C). Next, the inside of the casing 91 is
filled with a low refractive index curable resin solution 96
uncured that is to provide a cladding. Light curing, heat curing,
or any other method may be adopted to cure the curable resin
solution 96. Thus, the curable resin solution 96 having filled the
inside of the casing 91 is all cured into a cured material 96c,
thereby forming optical waveguides, one of which has the high
refractive index cured material 95c serving as the core and the
other of which has the low refractive index cured material 96c
serving as the cladding (FIG. 4D).
[0009] Thereafter, for example, a light emitting device 97 and a
light receiving device 98 are attached to the vicinities of the
junctions between the cured materials 95c serving as the cores and
the casing 91 made of transparent resin. Thus, an optical module
900 capable of single-line two-way communication can be completed
(FIG. 4E).
[0010] In the optical module 900 of FIG. 4E, the light emitting
device 97 and the light receiving device 98 face the cured
materials 95c serving as the cores via the casing 91 made of
transparent resin. With such a structure, it turns out, the
following problem arises when a life and a deterioration in
characteristics as a module are evaluated based on a so-called
acceleration test. That is, in the state where the load of normal
humidity at 85.degree. C. or 95% relative humidity at 75.degree. C.
is applied, it turns out, the bonding between the cured material
95c serving as the core and the optical device 97, 98 is
deteriorated in several hours, so that a light transmission loss is
lost on the order of 40%. This is caused mainly by separation of
the cured resin from the casing.
SUMMARY OF THE INVENTION
[0011] Thereupon, the inventors have earnestly examined an optical
module having a self-forming type core in a different configuration
from those of FIGS. 4A to 4E and have finally completed the
invention. That is, an object of the invention is to provide an
optical module in which the bonding between a core made of cured
resin and an optical device is not easily deteriorated.
[0012] To solve the aforesaid problem, according to the invention,
a method of manufacturing an optical module comprises holding
detachably the optical waveguide and at least one optical devic by
a mold, holding an uncured light curable resin in the mold,
emitting light of a wavelength for curing the light curable resin
from a leading end of the optical waveguide to the light curable
resin and curing the light curable resin to form a core, and
connecting the optical waveguide and the optical device by the
core. Besides, the method further comprises removing an uncured
part of the light curable resin from a surface of the core, and
covering the leading end of the optical waveguide, an exposed
surface of the core, and the optical device with a cladding
material. Besides, the mold is detached after the core is formed.
Besides, the core is formed after at least one optical component
such as a mirror, half mirror is held on the mold. Here, an optical
waveguide that is manufactured by any method. Besides, in the case
of a plurality of the optical devices, it is derived that the core
requires the number of branches smaller by one than the number of
the optical devices. Besides, any number of curved portions can
also be formed by using the mirrors. In the case of one optical
device, the number of mirrors, half mirrors, and other optical
components may be zero. The optical devices refer to a light
emitting device, a light receiving device, an optical modulator, a
coupler, and other devices.
[0013] Besides, the uncured resin removal step is carried out after
the optical waveguide, the any number of mirrors, half mirrors, and
other optical components, the one or plurality of optical devices,
and the waveguide, which is formed so as to integrally connect them
together and is branched and/or bent according to need, are
detached from the mold. As aforesaid, in the case of one optical
device, the number of mirrors, half mirrors, and other optical
components may be zero.
[0014] Besides, the cladding material includes a light curable or
heat curable resin, and the exposed surface of the core is covered
with the light curable or heat curable resin uncured, which resin
is thereafter cured. Besides, the optical component and the optical
device are fixed as the cladding material covers main portions
thereof and as the cladding material covers a vicinity of the
emitting end of the optical waveguide. Here, that the cladding
material covers the main portions of the optical components and
optical devices means that the cladding material covers them to a
sufficient extent to fix them, and is not limited to the state in
which the cladding material fully covers them.
[0015] Besides, an optical module comprises an optical waveguide, a
core that is formed in a self-forming manner by light curing as
light is emitted from a leading end of the optical waveguide, an
optical device connected to an other end of the core, and a
cladding that, made of resin cured to integrally cover the leading
end of the optical waveguide, the core, and the optical device.
Besides, polymerization of the core and the cladding material
proceeds due to heating, and the contraction ratio of the cladding
material is higher than that of the core.
[0016] Besides, the mold comprises an opening in the upper side
thereof, and a drain port which is provided in a bottom of the mold
to drain an uncured resin, wherein an end of the optical waveguide
is inserted into the mold in a horizontal direction, and wherein a
formed resin component and the optical waveguide is detached from
the mold in a state where the resin component and the optical
wavegude are held connected. Besides, the method of manufacturing
an optical module further comprises inserting one end of the
optical waveguide into the mold in a horizontal direction, putting
the optical device into the mold through an opening of the mold and
fix the optical device temporarily, introducing the light curable
resin into the mold, emitting a light beam at a wavelength adapted
to harden the curable resin, from an other end of the optical
waveguide into the mold, thereby to form the core which extends
from the one end of the optical waveguide inserted into the mold,
to the optical device, opening a drain port in a bottom of the
mold, draining an uncured part of the light curable resin from the
drain port, releasing a temporary fixation of the optical device
connected by the core, and introducing a cladding material into the
mold, curing the cladding material, and taking a optical module
having the optical waveguide and the optical device integrated by
the cladding material out of the mold. Besides, the curable resin
is introduced after any desired number of reflective mirrors,
semitransparent mirrors or other optical components have been put
into the mold through the opening of the mold and have been
temporarily fixed. Here, in the case where the plurality of optical
devices exist, it is derived that the core requires a branch or
branches the number of which is smaller by one than that of the
optical devices. Also, any desired number of bent portions can be
formed by employing the mirror or mirrors. In the case of the
single optical device, none of the reflective mirror,
semitransparent mirror and other optical component may well be
disposed. The "optical device" signifies a light emitting device, a
light receiving device, a light modulating device, a photocoupler,
or the like.
[0017] Besides, an apparatus for manufacturing an optical module of
the invention comprises a mold which has an opening and is capable
of draining an uncured resin from a drain port that is provided in
a bottom of the mold, wherein one end of the optical waveguide is
insertable into the mold in a horizontal direction, and a formed
resin component and the optical waveguide are detachable from the
mold in a state where the resin component and the optical waveguide
are connected to each other, a jig for putting at least one optical
device into the mold through the opening of the mold so as to
temporarily fix the optical device, means for introducing a light
curable resin for forming a core into the mold, means for guiding a
light beam at a wavelength adapted to cure the light curable resin,
from an other end of the optical waveguide into the mold, means for
introducing a cladding material into the mold, and means for curing
the cladding material, wherein the optical waveguide and the
optical device are connected by a core formed from the light
curable resin, and covered with the cladding material.
[0018] The invention makes it possible to provide an optical module
that uses a self-forming type core, wherein the core and optical
devices are not easily separated. According to the invention, the
optical devices can be pre-aligned in position, so that the process
is simplified, thus enabling a reduction in cost. Besides, since a
resin reservoir for a curable resin for core formation and a mold
for clad formation are made common, the process can be simplified.
Besides, the core can be bonded directly to the optical devices and
not via the casing, thus improving bonding efficiency, so that a
device life can be lengthened and a deterioration in
characteristics can be suppressed.
[0019] The detachable fixing member may be detached at any step,
but when it is detached before the uncured resin removal step, the
uncured resin can be properly removed. When the cladding material
uses a light or heat curable resin, especially a liquid one, the
core can be fully covered therewith, thus making it possible to
restrain light from leaking through a core surface. The cladding
material also covers the mirrors, half mirrors, and other optical
components, the main portions of the optical devices, and the
vicinity of the emitting end of the optical waveguide, thereby
making it possible to provide a strong optical module that is
difficult to break.
[0020] Besides, the core can be bonded directly to the optical
devices and not via the casing, thus improving bonding efficiency,
so that a device life can be lengthened and a deterioration in
characteristics can be suppressed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIGS. 1A to 1D are process diagrams showing in conceptual
form a manufacturing method of the invention
[0022] FIG. 2A is a perspective oblique view showing a fixing
member configured of two mold forms; FIG. 2B is an oblique view
showing an optical module main portion having optical components
connected by a core 6c made of a cured light curable resin;
[0023] FIG. 3A is a graph chart showing a change in optical
characteristics resulting from an acceleration test on bonding to a
light emitting device; FIG. 3B is a graph chart showing a change in
optical characteristics resulting from an acceleration test on
bonding to a light receiving device;
[0024] FIGS. 4A to 4E are process diagrams showing an optical
module manufacturing method described in JP-A-2002-365459;
[0025] FIGS. 5A to 5D are process diagrams (plan views) showing in
conceptual form a manufacturing method of the invention;
[0026] FIG. 6 is a perspective view showing an example of a mold
for use in the invention; and
[0027] FIGS. 7A to 7C are process diagrams (side views) showing
some steps of the manufacturing method in the case of using the
mold in FIG. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] Any optical components, etc. can be used to put the
invention into practice. The pre-formed optical waveguide can
suitably use an optical fiber such as a plastic optical fiber (POF)
or a glass optical fiber (GOF). Other than the so-called
fiber-shaped optical waveguide, however, any optical waveguides
capable of emitting light in a beam form as described later are
acceptable regardless of their shape. When an optical waveguide
whose cladding portion is easy to process is used out of them, as
described later, the processed cladding portion of the POF is
covered with a cladding material of a self-forming type optical
waveguide, whereby it is easy to make it difficult that the POF
comes off the optical module.
[0029] Any available light curable resin can be used to form the
core. For example, in JP-A-2002-169058 and JP-A-2002-149579, light
curable resins and polymerization initiators of radical
polymerization type and cationic polymerization type are listed as
examples in which they are used as two-component mixtures. However,
any one kind of the light curable resins described in
JP-A-2002-169038 and JP-A-2004-149579 can be used independently as
the light curable resin for forming the core of this application.
To reinforce the adhesion between the core end face of the optical
fiber and the device surfaces of the optical devices, as described
in JP-A-2002-365459, a silane coupling agent may be used by
dissolving or dispersing it in a light curable resign solution. The
cladding material can similarly use any one kind of the light
curable resins and polymerization initiators described in
JP-A-2002-169038 and JP-A-2004-149579, or otherwise may use a heat
curable resin.
FIRST EMBODIMENT
[0030] FIGS. 1A to 1D are process diagrams showing in conceptual
form a manufacturing method according to a first embodiment of the
invention. First, a POF 1, a green PD (light receiving device) 2, a
red LED (light emitting device) 3, and a wavelength selective
mirror 4 are prepared. The method uses the wavelength selective
mirror 4 that reflects red light and transmits green light. These
optical components are disposed on a fixing member 5 to which are
fixed a core end face 11 of the POF 1, a light receiving surface of
the light receiving device 2, a light emitting surface of the light
emitting device 3, and a reflective surface of the wavelength
selective mirror 4, and from which the optical components are
detachable. The fixing member 5 is configured such that a light
curable resin solution 6 to provide a core can be disposed thereon
between the core end face 11 of the POF 1 and the lower left
surface of the wavelength selective mirror 4, between the upper
right surface of the wavelength selective mirror 4 and the light
receiving surface of the light receiving device 2, and between the
lower left surface of the wavelength selective mirror 4 and the
light emitting surface of the light emitting device 3. This
configuration is conceptually shown as in FIG. 1A. The shape of the
entire fixing member 5 and the shape of a portion thereof in which
the light curable resin solution 6 is disposed, an example of which
shapes will be described in FIG. 2 and the subsequent figures, are
merely conceptually shown by broken lines in FIGS. 1A to 1D.
[0031] A POF having a core diameter of 980 .mu.m and an NA of 0.30
is used as the POF 1. By using "UVX-4037" made by Toagosei Co.,
Ltd., which is an acrylic resin, as the light curable resin
solution 6, a laser beam of 458 nm wavelength is irradiated into
the light curable resin solution 6 from the POF 1, thereby forming
a shaftlike cured material 6c that has branches in the vicinity of
the wavelength selective mirror 4. The shaftlike cured material 6c
is formed to provide connections between the core end face 11 of
the POF 1 and the lower left surface of the wavelength selective
mirror 4, between the upper right surface of the wavelength
selective mirror 4 and the light receiving surface of the light
receiving device 2, and between the lower left surface of the
wavelength selective mirror 4 and the light emitting surface of the
light emitting device 3 (FIG. 1B). The factor of curing into a
shaftlike form lies in that the light curable resin solution 6 is
increased in refractive index by curing. In fact, the "UVX-4037"
has a refractive index of 1.471 before curing and a refractive
index of 1.491 after curing.
[0032] Thereafter, the fixing member 5 is detached and the light
curable resin solution 6 uncured is removed (FIG. 1C). Thereafter,
the formed module main portion is put in another mold for example,
and the surrounding area thereof is covered with a cladding
material 7, which is cured. Thereby, an optical module 100 capable
of single-line two-way communication can be formed with ease.
Incidentally, "OP-38ZT", which, made by Dainippon Ink and
Chemicals, Inc., is a light curable fluorinated acrylic resin, is
used as the cladding material 7. The "OP-38ZT" has a refractive
index of 1.380 after curing.
[0033] A combination of upper and lower two mold forms M1 and M2 as
shown in FIG. 2A is adopted as the fixing member 5. When the mold
forms M1 and M2 are combined together, a portion 1m for fixing the
POF 1, a portion 2m for fixing the light receiving device 2, a
portion 3m for fixing the light emitting device 3, a portion 4m for
fixing the wavelength selective mirror 4, and a portion 6m to be
filled with the light curable resin solution 6 are formed as a
continuous cavity. For example, since the shaftlike core 6c can be
formed to have a diameter of 1 .mu.m, the portion 6m to be filled
with the light curable resin solution 6 is set to the size of the
order of 2 .mu.m in diameter. The reason is that, since the
invention is not of injection molding type, the diameter of the
portion 6m to be filled with the light curable resin solution 6
need be set larger than the designed diameter of the shaftlike core
6.
[0034] By using the fixing member 5 as shown in FIG. 2A, the core
6c is formed according to the process diagram of FIGS. 1A to 1D,
which then results in formation of an optical module main portion
as shown in FIG. 2B. It is apparent that the configuration of FIG.
2B is the same as that of FIG. 1C. In FIG. 2A, the cladding portion
of the POF 1 is processed into a two-step flangelike form in order
to prevent the POF 1 from coming off. This processing works
effectively both when the POF 1 is fixed to the fixing member 5 as
shown in FIG. 2A and when the entire module is covered with the
cladding material shown in FIG. 1D, thus making it possible to
prevent the POF 1 from coming off.
[0035] As a comparative example of the optical module 100 of the
invention formed as aforesaid, according to the process of FIGS. 4A
to 4E, a POF 91, a red LED 97, a green PD 98, and a wavelength
selective mirror 94 are prepared as the same optical components,
and an optical module 900 is formed using the "UVX-4037" as a core
and the "OP-38ZT" as a cladding. Then, an acceleration test is
performed to the optical module 100 and the optical module 900,
thus evaluating a change in optical characteristics. The results
are shown in FIGS. 3A and 3B. The vertical axis of FIGS. 3A and 3B
indicates 0 in the condition before the acceleration test, a
positive when an optical loss occurs, and a negative when a gain
occurs.
[0036] As shown in FIG. 3A, as for red light from the red LED 3, 97
to the POF 1, 91, in the optical module 100 of the invention, there
is almost no change in optical characteristics at normal humidity
at 85.degree. C. On the contrary, in the conventional optical
module 900, the optical characteristics deteriorate 2 dB or more at
normal humidity at 85.degree. C. (a 40% decrease in the amount of
light). Besides, in the optical module 100 of the invention, a gain
occurs at 95% relative humidity at 75.degree. C. The reason seems
to be that heating allows polymerization to proceed in both the
core 6c and the cladding 7, thus improving the bonding to the red
LED 3. Besides, as shown in FIG. 3B, the green LED 2 is also
similar in the change of optical characteristics to the red LED 3.
Thus, according to the invention, it is possible to easily provide
the optical module in which no separation between the core and the
optical device occurs due to heating and no deterioration in
characteristics occurs.
[0037] The gain is considered to occur at 95% relative humidity at
75.degree. C. for various reasons and, for example, there is the
following possibility. First, the core 6c is in the state where it
includes some amount of unpolymerized material when being cured and
formed in a self-forming manner. Next, when the cladding material 7
is light-cured, the unpolymerized material of the core 6c is
polymerized. On the contrary, the cladding material 7, merely
light-cured, is still in the state where it includes an
unpolymerized material. When the optical module 100 in such a state
is placed in a heated state, curing of the cladding material 7
proceeds. Thereby, the contraction in volume of the cladding
material 7 by polymerization of the unpolymerized material is made
larger than that of the core 6c by polymerization of the remaining
unpolymerized material. Thus, it is highly possible that
compressive stress occurs between the core and the optical
device.
[0038] The aforesaid embodiment shows an example in which the
combination of upper and lower two mold forms M1 and M2 provides
the fixing member 5, which is detached at the uncured resin removal
step. However, the fixing member of the invention is not limited to
this configuration. The combinational fixing member can be modified
in various ways so as to be capable of easy conception. For
example, the configuration may be such that the mold forms used to
cure the core 6c are used in curing the cladding material. In the
aforesaid embodiment, to suppress the consumption of the light
curable resin forming the core, the portion 6m to be filled with
the light curable resin solution 6 is made small in volume.
However, as shown in the conceptual diagram of FIG. 1A, the portion
6m may be large in volume.
[0039] The aforesaid embodiment shows an example in which the
optical components are not positionally aligned in the fixing
member 5. Alternatively, the configuration may be such that the
optical components are positionally aligned using an optical jig.
The aforesaid embodiment uses one wavelength selective filter, one
light emitting device, and one light receiving device.
Alternatively, the optical module may be configured in the
following manners by using a plurality of the wavelength selective
filters. That is, light from any number of light emitting devices
is collected and led to the POF etc. through the wavelength
selective filters. Besides, incident light is branched through the
wavelength selective filters, from the POF etc. to any number of
light receiving devices, by selecting or not selecting a
wavelength.
SECOND EMBODIMENT
[0040] FIGS. 5A to 5D are process diagrams showing in conceptual
form a manufacturing method according to a second embodiment of the
invention. First, a POF 1, a green PD 2, a red LED 3, and a
wavelength selective mirror 4 are prepared. The method uses the
wavelength selective mirror 4 that reflects red light and transmits
green light. The individual components are arranged within a mold
105 in such a way that the core end face 11 of the POF 1 is fixed
by the mold 105, and that the light receiving face of the light
receiving device 2, the light emitting face of the light emitting
device 3 and the reflective surface of the wavelength-selective
mirror 4 are temporarily fixed by jigs not shown. By the way,
whereas FIG. 4 depicts side views showing the process in a
horizontal direction, the respective views of FIG. 5 are side views
showing the process from above. Within the mold 105 indicated by a
broken line in FIG. 5, a curable resin liquid 6 to become a core
could be arranged. Incidentally, as will be indicated below, the
core 6c to be hardened and formed in self-forming fashion is formed
between the core end face 11 of the POF 1 and the left lower
surface of the wavelength-selective mirror 4, between the right
upper surface of the wavelength-selective mirror 4 and the light
receiving face of the light receiving device 2, and between the
left lower surface of the wavelength-selective mirror 4 and the
light emitting face of the light emitting device 3. This
configuration is conceptually shown as in FIG. 5A. The shape of the
entire mold 105 and the shape of a portion thereof in which the
light curable resin solution 6 is disposed, an example of which
shapes will be described in FIG. 6 and the subsequent figures, are
merely conceptually shown by broken lines in FIGS. 5A to 5D.
[0041] A POF having a core diameter of 980 .mu.m and an NA of 0.30
is used as the POF 1. By using "UVX-4037" made by Toagosei Co.,
Ltd., which is an acrylic resin, as the light curable resin
solution 6, a laser beam of 458 nm wavelength is irradiated into
the light curable resin solution 6 from the POF 1, thereby forming
a shaftlike cured material 6c that has branches in the vicinity of
the wavelength selective mirror 4. The shaftlike cured material 6c
is formed to provide connections between the core end face 11 of
the POF 1 and the lower left surface of the wavelength selective
mirror 4, between the upper right surface of the wavelength
selective mirror 4 and the light receiving surface of the light
receiving device 2, and between the lower left surface of the
wavelength selective mirror 4 and the light emitting surface of the
light emitting device 3 (FIG. 5B). The factor of curing into a
shaftlike form lies in that the light curable resin solution 6 is
increased in refractive index by curing. In fact, the "UVX-4037"
has a refractive index of 1.471 before curing and a refractive
index of 1.491 after curing.
[0042] Thereafter, a drain port in the bottom of the mold 105 is
opened and the light curable resin solution 6 uncured is removed
(FIG. 5C). Thereafter, the mold 105 is washed, and is filled up
with a clad material 7, which is subsequently hardened. In this
way, an optical module 100 capable of single-wire two-way optical
communications can be formed with ease (FIG. 5D). Incidentally,
"OP-38ZT", which, made by Dainippon Ink and Chemicals, Inc., is a
light curable fluorinated acrylic resin, is used as the cladding
material 7. The "OP-38ZT" has a refractive index of 1.380 after
curing.
[0043] Usable as the mold 105 is a substantially rectangular one
which has no top surface and has an opening above as shown in FIG.
6. The mold 105 is so constructed that the bottom 105B is slidable
in the lengthwise direction of this mold, and that a bottom surface
inside this mold can be entirely opened. A part 105' of the front
surface of the mold 105 is detachable. The front surface of the
mold 105 is provided with a recess 1H in the shape of the side
surface of a semicircular column, and it forms a support portion
for the POF 1 together with the recess 1H' of the part 105' in the
shape of the side surface of the semicircular column. The columnar
side surfaces of the recesses 1H and 1H' define a columnar side
surface of radius R, and this columnar side surface is formed so as
to agree with the outer peripheral surface of the POF 1. Besides,
the mold 105 and its part 105' have their connection surfaces
formed into a packing, and when they are combined, the resin liquid
filling up the interior of the mold 105 is prevented from leaking
out.
[0044] A process chart in the case of employing the mold 105 in
FIG. 6 is illustrated as side views (sectional views). FIG. 7A
shows a state where the bottom 105B of the mold 105 is closed,
where the POF 1 is fixed by the detachable part 105', where the
green PD 2, red LED 3 and wavelength-selective mirror 4 are
temporarily fixed by the respective jigs 2H, 3H and 4H, and where
the mold 105 is filled up with the unhardened curable resin 6. FIG.
7A corresponds to FIG. 5A. Incidentally, the wiring electrodes of
the green PD 2 and red LED 3 are omitted from illustration.
[0045] FIG. 7B shows a state where the bottom 105B of the mold 105
is slid and opened, and where the unhardened resin is removed. FIG.
7B corresponds to FIG. 5C.
[0046] FIG. 7C shows a state where the bottom 105B of the mold 105
is slid and closed, and where this mold is filled up with the clad
material 7. When the clad material 7 is hardened in the state of
FIG. 7C, the optical module 100 in FIG. 5D could be formed. The
detachable part 105' is detached as shown in FIG. 6, whereby the
optical module 100 could be easily taken out of the mold 105.
[0047] In the above example, the mold 105 whose bottom 105B is
slidable is employed, but the mold may be provided with means
capable of removing the unhardened curable resin, in its bottom.
Incidentally, an alternative drain port may well be in such a shape
that the unhardened curable resin is drawn out upwards from a
nozzle. The jigs for the temporary fixations may be any articles
which can position the optical devices and optical component. These
jigs may be demounted either in advance of the removal of the
unhardened curable resin, or midway of filling up the mold 105 with
the clad material 7.
[0048] The above example included one wavelength-selective filter,
and one light emitting device as well as one light receiving
device. It is also allowed, however, to construct an optical module
in which a plurality of wavelength-selective filters are employed,
whereby lights from any desired number of light emitting devices
are collected and guided to a POF or the like, or input light is
branched from a POF or the like into any desired number of light
receiving devices with or without the selection of wavelengths.
[0049] In case of constructing an optical module in which a green
LED and a red PD are respectively substituted for the green PD 2
and red LED 3 of the foregoing optical module 100, and employing
these optical modules in combination, a two-way optical
communications module in which lights of two wavelengths are
separately used for up and down communications can be formed with
ease. Incidentally, the wavelength characteristics of the light
receiving devices and light emitting devices and those of the
wavelength-selective mirrors can be selected and applied at
will.
* * * * *